This invention relates to electrical wiring boxes and electrical wiring cable clamp devices. More particularly, it is concerned with cable clamp inserts for electrical wiring boxes for use with non-metallic sheathed cable.
To relieve strain upon wiring connections to devices mounted in electrical wiring boxes, it is the general practice to clamp the cable at the point where it enters the box. Previously known clamp devices are of types which either fasten into the wiring box knock-out or attach to the wall of the box by means of a screw or bolt. In the case of the latter type of clamp, the cable, passing through a knockout opening in the wall of the box, is clamped between a wall of the box and a yoke tightened against the box wall. These yoke-type clamps require threaded openings in the box wall for their attachment, a feature which adds to the overall cost of the finished box and the time required for its installation. Moreover, suppliers of electrical wiring boxes generally furnish such clamps already in place at each knock-out to minimize installation time. This practice further adds to the cost of electrical wiring boxes employing this type of clamp.